I told them I can't get fish if I can't fit their needs and my parents said "They look happy in those tanks, so their fine." I cannot convince them. I realize my fish need help and I just won't buy any more fish until I get the right tank from now on. I can see why your all mad, I'm just as mad at myself as any of you are if not more because I can't do anything to save the fish. I'm honestly sorry.
A single betta CAN do fine in a 1 gallon tank. Provided that the water is maintained in that tank. As for longevity of a betta, provided perfect lab conditions and exercised daily I have read of bettas living up to 10 years old. If you have no choice but to keep a betta in a 1g tank which apparently is the case, do a 50% change of water at a minimum of once a week, preferably twice a week. Feed it regularly but don't overfeed. Also, you need to suck out the uneaten food with a turkey baster. Furthermore, the tank needs to be both heated and filtered regardless of what anyone else told you.
Putting two betta females together will almost undoubtedly get one killed. When there are a group of females together it allows some of the aggression to be spread out between the non dominant females. Putting a betta or platie with cichlids will just get them killed.
A 95% stocked 65 gallon tank could fit a large number of fish safely. Small fish like platies and bettas add almost nothing to the bio load of a tank. Any fish in a tank that is too small for them will be aggressive simply because there isnt enough room.
Further advice for residing on this forum:
Saying "I hope my fish gets eaten" or "I hope it dies" will SERIOUSLY tick people off.
Continuing to acquire fish when its already established that you don't have the resources to take care of them will also tick people off.
Don't use your age as an excuse, instead use this as a chance to show your parents that you are mature enough now to handle the responsibility of doing outside jobs. Mowing a few people's lawns or doing whatever grunt labor is required while maintaining your normal lifestyle will reinforce this. Sit your mom or dad down and talk to them like equals. I don't believe for a second that they will shut it down if you explain to them in an adult manner how things are.
Pointing out other people's mistakes isn't a good response. The vast majority of people have made their mistakes, learned from them, and moved on to not doing the same thing. On the other hand you continue making the same mistakes. You have at your access an amazing resource in this community full of knowledgeable people willing to help, ask us before you buy more fish.